The signature file contains the contents of the original data, and the original data is output to "originalFile.dat".

The openssl rsautl command signs the data directly, and therefore the maximum amount of data that can signed is very small. (To sign any amount of data, use openssl dgst -sign.) The maximum amount of data that can be signed (with rsautl) is the key size minus the overhead for the padding. The overhead size depends on the padding. With OAEP padding, the overhead is 42 bytes. With the default PKCSv1.5 padding, the overhead is 11 bytes.

Given a 2048-bit RSA key (256 bytes) and using PKCSv1.5 padding, the max data size that can be signed is 256 - 11 = 245 bytes.